ECE450H1S Software Engineering II Tutorial I Web Services

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1 Tutorial I Web Services 1. What is a Web Service? 2. An example Web Service 3. OmniEditor: Wrapping a text editor into a WS 4. OmniGraphEditor: supporting a graphic editor References Gustavo Alonso, Fabio Casati, Karumi Kuno, Vijay Machiraju. Web Services, Concepts, Architectures and Applications. Springer-Verlag, OmniEditor is a result of the course project for CSC408H.

2 What is Web Service Historic perspectives Centralized versus Distributed Programming Models: Client/Server, Master/Slave, SPMD, etc Middleware architecture 2-tier, 3-tier, n-tier Technical evolution IPC (inter process call): RPC, Java RMI, CORBA, DCOM Shared Memory, Distributed Shared Memory and Message Passing Interoperability, interoperability, interoperability

3 What is a Web Service? Web Services Standards (XML-based) SOAP (Simple Object Access Protocol) WSDL (Web Service Description Language) UDDI (Universal Description, Discovery, Integration) WS-I (integration), WS-Policy, WS-Security, etc. Chances and Challenges Application Wrappers to WS Web Services Compositions Holy Grail: large reusable library of WS with interoperability: 1,000 public WS ~ 1 Million private WS ROI (Return of Investments): > 10x? Issues: Privacy, Security, Performance

4 An example web service xmethods provides a web services to get the stock price Example SOAP messages Structure of WSDL descriptions A program that invokes the web service

5 SOAP architecture Service requestor application object (OpenOME) Service provider application object (OmniGraphEditor) SOAP-based middleware response request SOAP-based middleware

6 Example SOAP message: request <?xml version="1.0" encoding="utf-8"?> <SOAP-ENV:Envelope xmlns:soap-env=" xmlns:soap-enc=" xmlns:xsi=" xmlns:xsd=" xmlns:ns="urn:xmethods-delayed-quotes"> <SOAP-ENV:Body SOAP- ENV:encodingStyle=" <ns:getquote> <symbol>ibm</symbol> </ns:getquote> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

7 Example SOAP message: response <?xml version="1.0" encoding="utf-8"?> <SOAP-ENV:Envelope xmlns:soap-env=" xmlns:soap-enc=" xmlns:xsi=" xmlns:xsd=" xmlns:ns="urn:xmethods-delayed-quotes"> <SOAP-ENV:Body SOAP- ENV:encodingStyle=" <ns:getquoteresponse> <Result>86.05</Result> </ns:getquoteresponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

8 WSDL architecture WSDL (url) WSDL compiler (client) WSDL compiler (server side) Service requestor Service provider stub stub SOAP-based middleware response request SOAP-based middleware

9 Example WSDL structure: message <?xml version="1.0" encoding="utf-8"?> <definitions name="quote xmlns:tns="urn:xmethods-delayed-quotes" name spaces > types <message name="getquoterequest"> <part name="symbol" type="xsd:string"/> </message> <message name="getquoteresponse"> <part name="result" type="xsd:float"/> </message> porttype, binding, service </definitions>

10 Example WSDL structure: porttype <?xml version="1.0" encoding="utf-8"?> <definitions name="quote" name spaces > types, messages, <porttype name="quoteporttype"> <operation name="getquote"> <input message="tns:getquoterequest"/> <output message="tns:getquoteresponse"/> </operation> </porttype> binding, service </definitions>

11 Example WSDL structure: binding <?xml version="1.0" encoding="utf-8"?> <definitions name="quote" name spaces > types, messages, porttype <binding name="quote" type="tns:quoteporttype"> <SOAP:binding style="rpc" transport=" <operation name="getquote"> <SOAP:operation soapaction=""/> <input> <SOAP:body use="encoded" namespace="urn:xmethods-delayed-quotes" encodingstyle=" </input> <output> <SOAP:body use="encoded" namespace="urn:xmethods-delayed-quotes" encodingstyle=" </output> </operation> </binding> service </definitions>

12 Example WSDL structure: service <?xml version="1.0" encoding="utf-8"?> <definitions name="quote" name spaces > types, messages, porttype, binding <service name="quote"> <port name="quote" binding="tns:quote"> <SOAP:address location=" </port> </service> </definitions>

13 Web Services Invocation <ns:getquote> <symbol>ibm</symbol> </ns:getquote> Xmethods WSDL getquote Client Program <ns:getquoteresponse> <Result>86.05</Result> </ns:getquoteresponse>

14 Invoking the web service gsoap/soapcpp2/samples/quote //gsoap ns service name: quote //gsoap ns service style: rpc //gsoap ns service encoding: encoded //gsoap ns service namespace: urn:xmethods-delayed-quotes //gsoap ns service location: int ns getquote(char *symbol, float *Result); /* quote.h */ /* quote.c */ int main(int argc, char **argv) { struct soap soap; float q; char *sym; if (argc > 1) sym = argv[1]; else { fprintf(stderr, "Usage: quote <ticker>\n"); exit(1); } soap_init(&soap); if (soap_call_ns getquote(&soap, " "", sym, &q) == 0) printf("\ncompany - %s Quote - %f\n", sym, q); else soap_print_fault(&soap, stderr); soap_end(&soap); soap_done(&soap); return 0; } %> quote IBM Company - IBM Quote %>

15 Reference Architecture 1: Client/Server Web service UPLOAD Emacs VIM channel channel DOWNLOAD Eclipse VIM Whenever upload is called, the state of the channel in the server is updated or a new channel is created, and only when the editors need to refresh the buffer, they pull the information (downloading). Make sure the difference between downloaded buffer and the current buffer can be displayed.

16 Web service VIM channel channel Reference Architecture 2 UPLOAD DOWNLOAD Peer-to-Peer Web service VIM UPLOAD DOWNLOAD Web service Eclipse channel channel UPLOAD DOWNLOAD channel channel Whenever upload is called, inform other editors involved in the channel to refresh the changed state.

17 The OmniEditor Web Service Tools you need: Axis-1_1, Jakarta Tomcat server /u/prof/yijun/software/axis-1_1 /u/prof/yijun/software/jakarta-tomcat A few implementations of the OmniEditor We put them in the ECF /u/prof/yijun/axis /u/prof/yijun/deployed Phase A. You need to study one of them to understand how it works. Phase B. You can develop your own, or modify the existing ones to a number of operations for the graph editor Phase C. You need to study invoke the web service in your graph editor.

19 An example requirements specification float getquote(string name); // precondition: name = ticker symbol // postcondition: return -1 if name does not exist float getquote(string name); // precondition: name = part of the full name // postcondition: return -1 if name doesn t exist, // -2 if multiple matches What are the Goal (purpose), Input, Output, Pre/postconditions and Exceptions?

20 Required functions for the OmniGraphEditor Web Services Upload Download Insert Delete Select (highlight) For each function, you may have several alternatives. You shall make decision based on non-functional requirements (quality attributes)

What is Web Service. An example web service. What is a Web Service?

What is Web Service. An example web service. What is a Web Service? What is Web Service Tutorial I Web Services 1. What is a Web Service? 2. An example Web Service 3. OmniEditor: Wrapping a text editor into a WS 4. OmniGraphEditor: supporting a graphic editor References